On the basis of earlier parallels between the rapid sensitivity changes that occur in very early dark adaptation, and the characteristics displayed by the decay of the late receptor potential at the moment stimulation of the receptor is terminated, it appears that the course of early dark adaptation is a direct reflection of the LRP change. Data have now been obtained from a rod monochromat that support the proposed relationship for the new case of intense stimulation of the rods, impossible to detect in normal subjects. Experiments are under way to study the relationship in the case of intense cone stimulation of normal subjects. Regular dark adaptation has been shown by Rushton and others to be a process that averages sensitivity over a field of receptors. If early dark adaptation occurs in the receptor itself, it should not reflect receptor averaging, as does regular dark adaptation. It is proposed to measure the effect upon early dark adaptation of placing test stimuli on bright versus dim locations in various patterns of light adapting fields to see if this expected distinction holds experimentally.